On Mon, Mar 13, 2017 at 04:36:26PM -0700, Song Liu wrote:
> For the raid456 with writeback cache, when journal device failed during
> normal operation, it is still possible to persist all data, as all
> pending data is still in stripe cache. However, the stripe will be
> marked as fail with s.log_failed. Thus, the write out from stripe cache
> cannot make progress.
>
> To unblock the write out in journal failures, this patch allows stripes
> with data injournal to make progress.
what about the parity part? if log failed, we should skip journaling the parity.
Thanks,
Shaohua
> The array should be read-only in journal failures. Therefore, pending
> writes (in dev->towrite) are excluded in this write (in delay_towrite).
>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
> drivers/md/raid5.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 3233975..447d9dd 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -3069,6 +3069,10 @@ sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous)
> * When LOG_CRITICAL, stripes with injournal == 0 will be sent to
> * no_space_stripes list.
> *
> + * 3. during journal failure
> + * In journal failure, we try to flush all cached data to raid disks
> + * based on data in stripe cache. The array is read-only to upper
> + * layers, so we would skip all pending writes.
> */
> static inline bool delay_towrite(struct r5conf *conf,
> struct r5dev *dev,
> @@ -3082,6 +3086,9 @@ static inline bool delay_towrite(struct r5conf *conf,
> if (test_bit(R5C_LOG_CRITICAL, &conf->cache_state) &&
> s->injournal > 0)
> return true;
> + /* case 3 above */
> + if (s->log_failed && s->injournal)
> + return true;
> return false;
> }
>
> @@ -4721,7 +4728,8 @@ static void handle_stripe(struct stripe_head *sh)
> /* check if the array has lost more than max_degraded devices and,
> * if so, some requests might need to be failed.
> */
> - if (s.failed > conf->max_degraded || s.log_failed) {
> + if (s.failed > conf->max_degraded ||
> + (s.log_failed && s.injournal == 0)) {
> sh->check_state = 0;
> sh->reconstruct_state = 0;
> break_stripe_batch_list(sh, 0);
> --
> 2.9.3
>
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